A Novel Microwave Axion-Detector

Detector-Workshop TUM Munich

O. Reimann for the MADMAX-Group June 01, 2016

Slide 2 O. Reimann / MPP

MADMAX*-Members

• Allen Caldwell

• Chris Gooch

• Armen Hambarzumjan

• Bela Majorovits

• Alex Milar

• Georg Raffelt

• Javier Redondo

• Olaf Reimann

• Frank Simon

• Frank Steffen

*: Not the official project name, proposed by J. Redondo

Slide 3 O. Reimann / MPP

Outline

• Axion detector: Motivation and concept

▫ The QCD-axion as a dark matter constituent

▫ The detection concept

• Axion-photon converter

▫ Principle

▫ First test system

▫ Planned system

• Microwave radiometer

▫ Comparison between photon- and heterodyne detection

▫ First tests

▫ Sensitivity in terms of axions

• Conclusion

Slide 4 O. Reimann / MPP

Motivation and Concept

Slide 5 O. Reimann / MPP

• We have a dark matter problem … ▫ It seems, there is a little

bit too much matter, but

we cannot find it!

Motivation

© ESO

Expected dark matter

distribution around the

Milky Way

Slide 6 O. Reimann / MPP

• We know that from:

Motivation

© NASA, ESA, John Hopkins University © Wikipedia

CMB anisotropies

Galactic rotation curves Gravitational lensing

© NASA, WMAP © NASA, WMAP

And so many more!

Slide 7 O. Reimann / MPP

• … and we have a strong CP problem!

(And of course much more problems)

: Theta angle of strong interaction

: Gluon field strength tensor

: Strong coupling constant

• Theta should be somewhere between –π and π, …

Motivation

Slide 8 O. Reimann / MPP

• … but from the neutron electric dipole moment

we know:

• Fine-tuning ????

Motivation

We are here!!! J. Redondo

Slide 9 O. Reimann / MPP

• Peccei-Quinn solution: ▫ A dynamical field? →

Motivation

J. Redondo

Slide 10 O. Reimann / MPP

• Peccei-Quinn solution: ▫ A dynamical field? →

Motivation

Coherent oscillation

around the minimum

→ New particle (Axion)

J. Redondo

Symmetry breaking

Slide 11 O. Reimann / MPP

• Axion properties: ▫ Pseudo scalar

▫ Spin-0

▫ Weak interaction with hadrons and photons

(mass and couplings are suppressed by ,

the PQ-symmetry breaking scale)

• Two problems with one solution ??? ▫ Assumptions: The axion solves the strong CP problem

The axion is the cold dark matter candidate

▫ CDM: Oscillating coherent (scalar) axion field

Motivation

J. Redondo

Slide 12 O. Reimann / MPP

• Different scenarios for the axion-field development:

Motivation

Scenario I:

Prediction for symmetry

breaking before inflation

Being experimentally covered

(e.g. ADMX, … )

Scenario II:

Prediction for symmetry breaking after inflation: decay of

strings and domain walls

Experimentally not covered

Slide 13 O. Reimann / MPP

• Scenario II: ▫ Mass range > 40µeV > 10GHz

• Cannot be covered by “standard” ADMX-concept ▫ ADMX is volume dependent

▫ Cavity length has to shrink was increasing frequency or

▫ Make use of higher harmonics, but then loss is increasing

• Search for new ideas ▫ Sandwich structure

Motivation

Slide 14 O. Reimann / MPP

• Let’s start from “axion-EM” action density:

• with

: EM-field tensor

: EM vector potential

: Current density

: Axion-photon coupling

: fine structure constant

Concept

Slide 15 O. Reimann / MPP

• Result: Axion-Maxwell equations

• Assumptions: ▫ Homogeneous axion field (at least meter-scale)

▫ No space charge

▫ No free current

▫ Static B-field

Concept

Slide 16 O. Reimann / MPP

• Calculating the wave function from A-M equations:

▫ One can do similar for the magnetic field strength

• Solution for the E-field:

▫ Oscillating “electrostatic” field

▫ Usual photon wave (two directions)

▫ No coupling between them

• One can try to measure “electrostatic” field (difficult)

• Or try to couple the field to the wave!

Concept

Slide 17 O. Reimann / MPP

Sandwich-System

Slide 18 O. Reimann / MPP

• Axion-photon mixing at dielectric surfaces in a static

magnetic field

• Making use of Axion-Maxwell equations to calculate the

photon power density

Principle

Slide 19 O. Reimann / MPP

• EM waves from axion/photon conversion and an

incident wave at a surface

From Axion-Maxwell Equations:

EIy1: Incident TEM wave

ETy2 : Transmitted TEM wave

ERy1 :Outgoing TEM wave

EPy : Electric field from axion conversion

Slide 20 O. Reimann / MPP

• Power density from axion/photon conversion at a surface

• “Related to transition radiation”

From Axion-Maxwell Equations:

BSy: Perpendicular magnetic field in T

gagg: Axion-model coupling constant

er: Relative dielectric constant

Sy: Generated signal intensity

Slide 21 O. Reimann / MPP

• Power density from axion/photon conversion at a

metallic surface

From Axion-Maxwell Equations:

BSy: Perpendicular magnetic field in T

gagg: Axion-model coupling constant

er: Relative dielectric constant

Sy: Generated signal intensity

Slide 22 O. Reimann / MPP

• Now we have the recipe for an axion-photon converter: ▫ “Axion-photon conversion” at dielectric surfaces

▫ Dielectric material is “transparent” for many but not all photons

→ small reflection

▫ Many surfaces building a “resonator”→ “photon boost”

Axion-Photon Converter (Sandwich-System)

J. Redondo

Slide 23 O. Reimann / MPP

• We define the (power) boost factor relative to the

signal from a metallic surface

• Some properties of the boost factor:

Axion-Photon Converter (Sandwich-System)

Boost factor

W ·

bandw

idth

Number of dielectrics (no mirror)

A. Milar

Slide 24 O. Reimann / MPP

• Important material properties: ▫ High dielectric constant

(for large axion/photon conversion factor)

▫ Low loss → low tan d

(in order to reduce photon loss)

▫ Stable

▫ Cheap

▫ → Sapphire (Al2O3)

▫ → Lanthanide Aluminate (LaAlO3)

Possible Dielectric Materials

© Wikipedia: Dielectric loss

Slide 25 O. Reimann / MPP

• Electromagnetic properties: ▫ High dielectric constant

▫ Low tan d

▫ Anisotropic

Sapphire (Al2O3)

z

For C-plane cut:

ε =

휀 0 0

0 휀 0

0 0 휀

휀 = 9.35

휀 = 11.53

@ 23°C

𝑡𝑎𝑛𝛿 =

𝑡𝑎𝑛𝛿 0 0

0 𝑡𝑎𝑛𝛿 0

0 0 𝑡𝑎𝑛𝛿

𝑡𝑎𝑛𝛿 = 3.010 ∙ 10−5 𝑡𝑎𝑛𝛿 = 8.610 ∙ 10−5

@ 23°C, f=10GHz

© Wikipedia

Slide 26 O. Reimann / MPP

• Temperature dependence:

Sapphire (Al2O3)

@ f=9GHz

@ f=25GHz?

Slide 27 O. Reimann / MPP

• Electromagnetic properties: ▫ Very high dielectric constant (e=23.7)

▫ Low tan d at low temperatures

• Temperature dependence:

Lanthanide Aluminate (LaAlO3)

@ f=18GHz?

@ f=18GHz?

(3) Czochralski-grown material

Slide 28 O. Reimann / MPP

• Example (broadband system): ▫ Constant dielectric thickness

▫ Frequency and bandwidth tuning by adjustable spacing

Adjusting the Resonator (Simulation)

20 dielectrics

εr = 24 (LaAlO3)

Bandwidth 250MHz

IMPORTANT:

Coupling between boost

factor and reflection,

transmission or group delay!!!

Slide 29 O. Reimann / MPP

• Principle setup:

Axion Detection System Resonator:

80 LaAlO3 plates

Spacing: mm to cm

Frequency range: 10 to 100 GHz Axion mass range: 40µeV to 400µeV

Magnet:

Dipole

B = 10T

Bore diameter: 1m

Slide 30 O. Reimann / MPP

• Principle setup (3D)

motor drive not shown:

Axion Detection System Resonator:

80 LaAlO3 plates

Spacing: mm to cm

Frequency range: 10 to 100 GHz Axion mass range: 40µeV to 400µeV

Parabolic mirror

Horn antenna

(to receiver)

Resonator

10T Magnet

Slide 31 O. Reimann / MPP

• First test resonator for simulation/measurement

comparison:

▫ Diameter: 100 ±0.2 mm

▫ Thickness: 650 ±20 μm

▫ Surface roughness: <1µm and < 0.3nm

Very First Test-Converter

Slide 32 O. Reimann / MPP

• New system has adjustable disk spacing

New Test System

Receiver horn

“Fake” axion

injection

Resonator (adjustable)

5 disks

different materials

Drive motors

(100nm accuracy)

Slide 33 O. Reimann / MPP

• Tuned to low frequency (low axion mass)

New Test System

Slide 34 O. Reimann / MPP

• Tuned to high frequency (high axion mass)

New Test System

Slide 35 O. Reimann / MPP

• The real device (200mm sapphire disks):

New Test System

Resonator (adjustable)

5(4) disks, sapphire

Drive motor

(100nm accuracy)

Receiver horn Parabolic

mirror

Waveguide system

(for background reduction)

Slide 36 O. Reimann / MPP

• First results (Transmission, 1…5 disks, manual adjustm.)

New Test System

10,0G 12,0G 14,0G 16,0G 18,0G 20,0G 22,0G 24,0G0,0

0,2

0,4

0,6

0,8

1,0

1,2

Measurement

Filtered Measurement

Simulation

Re

son

ato

r T

ran

sm

issio

n

Frequency (Hz)

10,0G 12,0G 14,0G 16,0G 18,0G 20,0G 22,0G 24,0G0,0

0,2

0,4

0,6

0,8

1,0

1,2

Measurement

Filtered Measurement

Simulation

Re

son

ato

r T

ran

sm

issio

n

Frequency (Hz)

10,0G 12,0G 14,0G 16,0G 18,0G 20,0G 22,0G 24,0G0,0

0,2

0,4

0,6

0,8

1,0

1,2

Measurement

Filtered Measurement

Simulation

Re

son

ato

r T

ran

sm

issio

n

Frequency (Hz)

10,0G 12,0G 14,0G 16,0G 18,0G 20,0G 22,0G 24,0G0,0

0,2

0,4

0,6

0,8

1,0

1,2

Measurement

Filtered Measurement

Simulation

R

eson

ato

r T

ran

sm

issio

n

Frequency (Hz)

1 Disk 2 Disks

5 Disks 4 Disks

Slide 37 O. Reimann / MPP

• First results (Reflection, 4 disks + 1 mirror)

New Test System

10,0G 12,0G 14,0G 16,0G 18,0G 20,0G 22,0G 24,0G-1,0n

0,0

1,0n

2,0n

3,0n

4,0n

5,0n

6,0n Measurement

Simulation (dD=10mm)

Gro

up D

ela

y D

iffe

rence (

s)

Frequency (Hz)

Nominal Antenna Range

>1 Mode

Slide 38 O. Reimann / MPP

Slide 39 O. Reimann / MPP

Photon Detection Setups

• Two principle ways: ▫ Photon counting

▫ Measurement of mean photon flux

• Photon counting ▫ Limited by photon energy

(Needs „high energy“ photons)

▫ Energy (frequency) resolution is limited

• Photon flux measurement ▫ Not limited by low energy photons

▫ Excellent frequency (energy) resolution (easily it can be better than 10-9), because of usually used “coherent” detection (normally heterodyne detection)

Slide 40 O. Reimann / MPP

• Photon counting:

• Photon flux measurement:

direct heterodyne (“coherent”)

Photon Detection Setups

G

fG

000

Mixer

Oscillator

Bandpass Detector Current

meter

Detector Current

meter

Detector Counter

Slide 41 O. Reimann / MPP

• Contribution of a detector:

(no phase preservation)

• Contribution of an amplifier or mixer:

(phase preservation)

• Limit for low frequencies and/or high temperatures:

Spectral Power Density of (BB)-Noise

Noise temperature

Slide 42 O. Reimann / MPP

• Example: ▫ Spectral power density for different temperatures

Spectral Power Density of (BB)-Noise

108 109 1010 1011 1012 1013 1014

10 22

10 21

10 20

10 19

Frequency (Hz)

EN(W

Hz-

1)

400 K

100 K

10 K

1 K

100 K

Amplifier, Mixer

Detector

“Quantum limit”

Slide 43 O. Reimann / MPP

• System noise temperature TSys and bandwidth DfF are

difficult to measure for broadband detectors

▫ Johnson noise

▫ Phonon-electron coupling

▫ Generation-recombination noise

▫ Background noise

▫ …

• → Using noise equivalent power (NEP):

• Sometimes a little bit different NEP definitions are used, most of them have factor 2 or 2½ included (Because of 2 polarizations or time to bandwidth conversion)

Noise Equivalent Power

Slide 44 O. Reimann / MPP

• Types of broadband detectors ▫ Bolometers

▫ Microwave kinetic inductance detector (MKID)

▫ Double quantum well detectors

▫ Transition edge sensors (TES)

• Usually they work good only at higher frequencies (> 50 … 100 GHz)

• Often the devices are background limited ▫ Example:

Background temperature 300 K, bandwidth 50 GHz → NEP = 9.2 10-16 W Hz-½

• Temperature and bandwidth can be reduced, but then again the other noise sources start to dominate (see later)!

Broadband detectors

Slide 45 O. Reimann / MPP

• Noise equivalent power of a heterodyne system:

Comparison: Heterodyne Direct Det.

LNF-LNC6_20B @ 8K

5 109 1 1010 5 1010 1 1011 5 1011 1 1012

10 21

10 20

10 19

10 18

Non-existing graphene

bolometer with 10 MHz coupling bandwidth and

20 mK temperature [1].

Unrealistic!!!

State-of-the-art

bolometer

Frequency (Hz)

NEP (

W H

z-½)

[1] K.C. Fong and K.C. Schwab, “Ultra-sensitive and Wide Bandwidth Thermal Measurements of Graphene at Low

Temperatures“, 2012

Slide 46 O. Reimann / MPP

• What is the detectable noise temperature for a given

system noise temperature (Dicke-formula):

• Detectable noise power (assuming no gain fluctuation)

• Averaging time for a given signal/noise ratio:

Choosing the Right Bandwidth

with and

with

DfF: Filter bandwidth

t: Averaging time

TSys: Total system noise temp.

Slide 47 O. Reimann / MPP

• What is the best bandwidth for line detection ▫ Detectable background noise power increases with frequency

(Square root)

▫ Signal noise increases with frequency

(Linear, if rect. distribution)

▫ → Bandwidth should not

be larger than line-

width for best signal-

noise ratio

Choosing the Right Bandwidth

0.0 2.0k 4.0k 6.0k 8.0k 10.0k 12.0k 14.0k 16.0k 18.0k 20.0k0.0

2.0x10-24

4.0x10-24

6.0x10-24

8.0x10-24

1.0x10-23

1.2x10-23

1.4x10-23

1.6x10-23

1.8x10-23

Integration time:

50h

100h

200h

400h

Signal

Sig

na

l a

nd

No

ise

Po

we

r (W

)

Filter Bandwidth (Hz)

Signal linewidth limitExample

Receiver: TSys=5K Signal: 10-23W (1photon/s @ 15GHz),

linewidth 10kHz, equal distributed

Slide 48 O. Reimann / MPP

• Noise temperature limit for InP devices: ▫ Mainly phonon self heating Inner bulk black body radiator

Heterodyne Detection: Real Devices

Shi, et. al.

A 100-GHz Fixed-Tuned Waveguide SIS Mixer Exhibiting Broad Bandwidth and Very Low

Noise Temperature, 1997

InP-HFET,

Bryerton et. al. “Ultra Low Noise Cryogenic Amplifiers for

Radio Astronomy”, 2013

InP-HEMT

Our amplifier, LNF

Slide 49 O. Reimann / MPP

• Axion mass range: 40 µeV … 400 µeV

Frequency range: 10 GHz … 100 GHz (l = 3 cm … 3 mm)

• Detection of signal line in frequency domain with

DA = 10-6 A

• Check noise level (Physical limit?)

• …

Heterodyne Detection: First Lab Test

Slide 50 O. Reimann / MPP

• 2 different devices

(Low Noise Factory,

Chalmer University)

• Same characteristics @ RT

but 1 is for cryo temperatures

Low-Noise Amplifiers

6-20 GHz Cryogenic Low Noise Amplifier, 5K @ 8-10K

1-15 GHz Low Noise Amplifier, 75K @ RT

cannot significantly reduced

(Nature Materials Nov. 10, 2014

© Low Noise Factory

Slide 51 O. Reimann / MPP

G

fLO1

G

fLO2

10 GHz 1.725 GHzSignal analyzer

35 dBT

N=75 K

19 dB

-10 dB

12GHz - 18 GHz

1. Local oscillator11.7GHz - 70GHz

2. Local oscillator1.7GHz

25 MHz

• First lab system:

Heterodyne Detection

Rubidium time standard to

synchronize all detection oscillators and samplers

1. Amplifier + high pass

Signal analyzer

(3 samplers)

1. local oscillator

Her the reality is a little bit

more complicated! (FT-analysis)

2. local oscillator

Slide 52 O. Reimann / MPP

• Inject fake axion signal with 3.10-21 W at room temp. ▫ Frequency: 15 GHz

▫ Detection bandwidth: 10 kHz

▫ One week measurement (integrate signal)

Heterodyne Detection: First Tests

0.595

0.6

0.605

0.61

0.615

0.62

0.625

x 10-9

1350 1360 1370 1380 1390

x 106

Independent „blind“ analysis

found > 6σ signal successfully

Factor 100

better at LHe

temperature

Slide 53 O. Reimann / MPP

Sensitivity in terms of Axions

80 disks (LaAlO3)

d=1m, B=10 T, t=200 h, DA=10-6 A

8K amplifier temperature

4s detection level

Slide 54 O. Reimann / MPP

• Coupling boost factor ↔ reflection, transmission, GD

• Optimal longitudinal field distribution and eR

• Algorithm and setup for optimal disk positioning

• Background ▫ Black body radiation from lossy elements

▫ Cosmic microwave background

▫ …

• Sampler dead time and quantization noise

• Data analysis

• Run optimization

• Magnet: ▫ Large bore 10T magnet (Challenging, but possible)

• …

Not discussed here (not enough time):

Slide 55 O. Reimann / MPP

• Resonant axion-photon detection using dielectric plates

is promising

• First tests have been successful

• Test to figure out the mechanical sensitivity is ongoing

• Receiver sensitivity is good enough

• “Broadband” measurement is possible

Conclusion

Thank you very much for patience